Number of options outstanding, including both vested and non-vested options.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Preferred and Common Stock - Schedule of Shares Outstanding and Weighted-Average Remaining Contractual Life by Exercise Range (Details) - $ / shares	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor (in Dollars per share)	$ 24.11
Exercise price range ceiling (in Dollars per share)	$ 44.39
Number of shares	291,200
24.11-25.26
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor (in Dollars per share)	$ 24.11
Exercise price range ceiling (in Dollars per share)	25.26
25.49-26.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor (in Dollars per share)	25.49
Exercise price range ceiling (in Dollars per share)	26.92
44.39
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor (in Dollars per share)	44.39
Exercise price range ceiling (in Dollars per share)	$ 44.39
Stock Options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	291,200	401,800	712,024	854,809
Weighted average exercise price (in Dollars per share)	$ 37.46	$ 36.55	$ 36.73	$ 34.64
Weighted average remaining contractual life (years)	4 years 3 months 26 days
Stock Options \| 24.11-25.26
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	84,350
Weighted average exercise price (in Dollars per share)	$ 25.23
Weighted average remaining contractual life (years)	3 years 1 month 12 days
Stock Options \| 25.49-26.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	22,500
Weighted average exercise price (in Dollars per share)	$ 26.47
Weighted average remaining contractual life (years)	1 year 9 months 21 days
Stock Options \| 44.39
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	184,350
Weighted average exercise price (in Dollars per share)	$ 44.39
Weighted average remaining contractual life (years)	5 years 2 months 12 days